Scrollbar Moving Automatically on Tree Expansion - in Java Swing's BasicTreeUI - Article 79 - go-pugleaf

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Scrollbar Moving Automatically on Tree Expansion - in Java Swing's BasicTreeUI

#79

From: naimish.parikh
Date: Thu, 29 Dec 2005 18:23

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Hi ,

My Problem:
When a tree item/row is expanded , the scrollbars of the tree
automatically move to ensure that the child of the tree item (which is
expanded) is visible.
I donot want the scrollbars to move when tree is expanded.  Is there
any way we can do it without extending/inheriting
javax.swing.plaf.basic.BasicTreeUI?

I use:
- Java Swing's MetalTreeUI and my own tree class derived from JTree.

This behaviour seems to be controlled by
BasicTreeUI.toggleExpandedState

 /**
     * Expands path if it is not expanded, or collapses row if it is
expanded.
     * If expanding a path and JTree scrolls on expand,
ensureRowsAreVisible
     * is invoked to scroll as many of the children to visible as
possible
     * (tries to scroll to last visible descendant of path).
     */
    protected void toggleExpandState(TreePath path) {
	if(!tree.isExpanded(path)) {
	    int       row = getRowForPath(tree, path);

	    tree.expandPath(path);
	    updateSize();
	    if(row != -1) {
		if(tree.getScrollsOnExpand())
		    ensureRowsAreVisible(row, row + treeState.
					 getVisibleChildCount(path));
		else
		    ensureRowsAreVisible(row, row);
	    }
	}
	else {
	    tree.collapsePath(path);
	    updateSize();
	}
    }




Thanks
Naimish Parikh

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Subject: Scrollbar Moving Automatically on Tree Expansion - in Java Swing's BasicTreeUI
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